After spending several hours on the net searching and debugging my site I finally solved the problem regarding the "operation aborted" issue in IE7. (IE crashed immediately after hitting my frontpage). Turned out I was looking too much into Virtuemart modules, not the core Joomla modules.
I stumbled upon a post on the Joomla forum describing an issue with "domready. Load" which is implemented into the core mod_mainmenu module. The following solved my problem:
Change the following file: /libraries/joomla/html/html/behavior.php
~line 108
$tooltipInit = ' window.addEvent(\'domready\', function(){ var JTooltips = new Tips($$(\''.$selector.'\'), '.$options.'); });';
to
$tooltipInit = ' window.addEvent(\'load\', function(){ var JTooltips = new Tips($$(\''.$selector.'\'), '.$options.'); });';
Alternatively they do describe some other possibilities utilising Moo 1.2.1. for the frontend, leaving Joomla backend on 1.1.1. I enclosed the link of the thread below for everybody who is interested.
http://forum.joomla.org/viewtopic.php?f=231&t=310784Hope this helps some of you as well.